Researchers from Children's Hospital Boston -- led by nutrition researcher Dr. David Ludwig -- analyzed 111 studies of beverages published between Jan. 1, 1999, and Dec. 31, 2003, and found that the rate of favorable findings in studies paid for by the beverage industry was much higher than that of non-industry-funded studies.
Ludwig and colleagues chose to focus their study on the beverage industry partly because soda, milk and juice drinks are all aggressively marketed to children. If the findings of an industry-sponsored study are skewed because of the source of the study's funding, children stand to be negatively affected.
"Conflicts of interest in pharmaceutical research could affect millions of people taking medicines," Ludwig said. "Conflicts of interest in nutrition research could affect the health of everyone because we all eat."
Ludwig's team examined the conclusions of the studies for favorable, neutral or negative results for the beverage industry, then checked the studies' funding. The researchers found that the beverage industry paid fully for 22 percent of the studies, while partly funding an additional 32 percent of studies.
When Ludwig and colleagues examined only studies that reached a positive conclusion, they found studies entirely sponsored with beverage industry money were up to eight times more likely to result in industry-favorable conclusions than studies not funded by the industry.
Ludwig's team also found that when the industry funded studies that directly affected participants' health -- such as giving them a drink and measuring health effects -- all studies reached industry-positive results, whereas 37 percent of such studies that were not funded by the beverage industry reached negative conclusions.
The American Beverage Association and the Dairy Council questioned the results of Ludwig's study, claiming his research was biased and incomplete. ABA president Susan K. Neely said Ludwig's study is "yet another attack on industry by activists who demonstrate their own biases in their review by looking only at the funding source and not judging the research on its merits."
However, New York University nutrition professor Marion Nestle said she was "glad" Ludwig published his study, because "food companies have only one purpose in funding research, and that's to use the results in marketing. If they can't use the results in marketing, then they're not going to fund it."